Posted
by
CmdrTacoon Tuesday March 08, 2011 @10:00AM
from the explains-my-wife's-navigation-system dept.

An anonymous reader writes "A simple $30 GPS jammer made in China can ruin your day. It doesn't just affect your car's navigation — ATM machines, cell phone towers, plane, boat, train navigation systems all depend upon GPS signals that are easily blocked. These devices fail badly — with no redundancy. These jammers can be used to defeat vehicle tracking products — but end up causing a moving cloud of chaos. The next wave of anti-GPS devices include GPS spoofers to trick or confuse nearby devices."

What's even more disturbing is that the FAA is currently looking to move away [nytimes.com] from traditional radar and even human air traffic controllers [theatlantic.com], as part of their "NextGen" system [faa.gov]. GPS is just fine as long as there is a redundancy in the system. But the idea of abandoning radar as if GPS were a time-tested system is a little scary.

I wonder how this would affect a plane landing if somebody set one off while flying on a plane right before touch down. Anybody know? Would the plane automatically abort? Would the pilot have enough time to manually take over? Would it crash?

It would affect nothing. Pilots have a "decision height" at which point they must go around if they can't see the runway. GPS, along with several other technologies, allows 2 things, a lower decision height, and automated landings. Rules that regulate pilots and avionics require that the pilot is always able to identify a failure, and to be reasonably able to safely recover from a failure using alternative instruments or procedures. If the plane's GPS were to loose a fix, it would set off an alarm, and the pilot would either immediately start a go-around, or s/he would choose to land manually.

Planes also have an IRU (internal reference unit) or laser gyroscope that is able to dead reckon where the plane is based on the fact of knowing where an aircraft was at some previous point, and summing up all of the movements of the aircraft since that point. Before GPS, using IRUs were the primary automated navigation tool for commercial aircraft. So even in the event of a loss of GPS fix, the aircraft still knows exactly where it is for a long period of time. I don't know if the IRU can feed its location fix back into the NextGen aircraft transponder (which normally uses GPS) that reports to air traffic control computers where the aircraft is.

Modern INS is good enough that even if you lose GPS lock, you'll be able to get where you're going very precisely. You can dead reckon very, very well with modern equipment.

I was recently flying a fairly expensive INS, and broke GPS lock in the middle of a flight. 3 hours of jet flight later, that INS showed me on the runway with the same 6-DOF (position, yaw, pitch, roll) within a couple of meters of what a still locked system was doing.

If you bothered to read past the first page, you would have found out that the $30 box from the evil empire was shutting down Newark Airport twice a day because a truck driver was using it to defeat the toll transponder on the NJ Turnpike next door.

the $30 box from the evil empire was shutting down Newark Airport twice a day because a truck driver was using it to defeat the toll transponder on the NJ Turnpike next door.

Which, incidentally, is another reason why all of these plans to replace gasoline taxes by levying road-use taxes based on in-car GPS monitoring devices are a really bad idea. It will create a massive demand for such jammers and they will get a lot more sophisticated than the current ones - coverage will be limited to a few feet, or even inches, and be essentially undetectable without physical inspection.

The ability to white-noise (or pink-noise) jam GPS has been around and employed for, literally, years. And, most of the first of these I saw came from China, too. GPS is a relatively fragile system, at least n the L1-C/A world: GPS satellites have limited power budgets so signal levels are low on the ground. Receivers have high gain. Multipath in urban environments can confuse receivers. Emitting a random noise signal over the range of L1 frequencies isn't that hard, and doesn't take much power... or antenna height... to cause problems.

The article makes all of these points. Read it and take note of the fragility of the system. That's its downfall, not a $30 device.

they can be used to trick china and great britain to the brink of war by fooling the royal navy into invading chinese waters. then a stealth boat can make the other side think someone is shooting missiles at them. all of course, so rupert murdoch, i mean, uh, elliot carver, can sell... newspapers!

And how can drugs be illegal if there's a guy that sells them in the local park. Just because they're out there doesn't change the legality. In this case the testing hasn't been completed, most likely it either doesn't have that impact or the devices will be yanked. The FCC doesn't allow devices to interfere in that way, so I'm guessing that somebody screwed up in evaluating them.

I'm not surprised by how many devices would use GPS(the ability to get a fairly accurate location fix and a damn accurate timebase for peanuts and an OK view of the sky is certainly attractive...); but I am surprised, a bit, at how many "serious" systems(even ones where hostile action is to be expected, like ATMs, or where failure Just Isn't Acceptable, like air traffic control) wouldn't have some degree of redundancy, if only because of the risk of a cheap GPS module burning some sensitive RF chip because the local arc-welder user fired up again...

Your basic RTC, say, isn't as accurate as GPS time; especially in the long term, or if not temperature compensated and subject to variable conditions; but it should still deviate by less than a second over a day or two of lost GPS(never mind 10-60 minutes of jamming) and can, if needed, retain reasonably accurate time for as long as power holds out, and they don't need much power.

Similarly, today's MEMS accelerometers and on-chip magnetometers/compasses, while you might not want to dead-reckon your way around the world with them, can easily enough compensate for losses in GPS fix over the short term, and can 'sanity-check' abrupt changes in GPS readings.

For static objects(like radar towers) you can basically treat position as a constant(possibly with recalibration from time to time if there are structural shifts) and calculate dish position based on a simple rotary encoder or the like.

Obviously, for space, power, and cost reasons, Joe Consumer's $50 cellphone or $80 dash-nav isn't necessarily going to incorporate multiple layers of GPS failsafe. If the GPS stops working, Joe can just use the meat-coprocessor he stores in his skull to suck it up and figure it out until GPS comes back online.

For more important systems, though, I would honestly have hoped for better, especially in situations(like cell towers and most ATMs) where the equipment itself isn't exactly inexpensive, so $50 or $100 worth of accelerometer and RTC failsafe would be reasonable, and where they usually have a network hard-line. NTP isn't perfect; but it certainly is handy(if necessary, users of dedicated circuits, rather than those who rely on public internet, might be able to achieve even greater accuracy by comparing their GPS time with the GPS time reported by the hardware on the other end of the circuit, to determine the round-trip time fairly exactly...)

Also, the "backup" gyrocompass mentioned in TFA, that failed to act as a backup to GPS because it crashed when it lost GPS signal is just sad. Perhaps it was purchased from the same company who provides emergency generators that can only be started by mains-powered control systems?

Finland has had plans to introduce a road toll system based on GPS. If that happens, spoofing/jamming GPS will save you a lot of money. As a side-effect of everyone using blocking devices, nobody will be able to navigate anymore:)

What competent engineer would design an important system that depends on GPS, with no backup? The satellite signals are very faint, and can be disrupted for seconds or hours by lots of different causes, including entirely natural causes like solar flares.

What competent engineer would design an important system that depends on GPS, with no backup? The satellite signals are very faint, and can be disrupted for seconds or hours by lots of different causes, including entirely natural causes like solar flares.

I was at a conference recently where Gen. Schwartz, Air Force Chief of Staff, brought up your point exactly. To combat jamming of a particular system, they are working to build redundant navigation systems into their weapons. So, for example, if GPS guidance fails maybe it switches over to laser guidance, if that fails maybe it switches over to INS.

I'm as critical of the war on terror as you are, but you have to remember the military's role in a democracy. It's not their job to decide when to go to war, with whom, for what reason. It is their job to *assume* the country's elected representatives have good reasons to go to war, and to prosecute that war as efficiently (in terms of lives and dollars) as possible.

Exceptions can be made for individual soldiers' conscientious objection, but that cannot apply to the military as an institution. If all it

I suspect that there is (in addition to any device-specific fallbacks, inertial, optical, radar, dead reckoning, whateer) one major factor that helps that be less of an issue:

Jamming/spoofing requires emitting an RF signal, typically one stronger than the legitimate one. There are weapons(such as the oh-so-cleverly named HARM [wikipedia.org] missile that are specifically designed to lock on to RF sources and follow them back to their transmitters.

A sufficiently clever opponent could(given the relative cheapness of GP

I want the next gen jammer with built in EMP, cell phone jammer, Universal tv/stereo remote and beer opener.Make it the Acme and not the Apple. The I-jam will have a per use fee and not work on I-phones.

Then my next missile will be a 100KiloTon yield. Jam away at 1000 watts, I'll be close enough to vaporize you.

Remember the answer to a technical foe is by being crude. They have a lot of tech to make your missile miss the target, make the missile big enough to include the target even at the widest miss.

OR, use guidance systems that are completely self-contained (inertial dead-reckoning, computer vision, etc.) so that GPS is completely irrelevant. Cruise missiles hit targets from substantial distances without having any need for GPS input.

Military has its own encrypted channels for GPS signals. Same satellites but not the same signal as consumer devices.

While this is true, it just means that you need to jam a different frequency. Encryption has nothing to do with it as you aren't trying to access it, but DoS it. The reasons that the military runs its own separate GPS are for better accuracy (civilian GPS has inaccuracy built in while military GPS is accurate to within a meter) and so they can shut it down without hurting themselves within a theater.

A quick GPS history lesson:
GPS signals are spread-spectrum in order to make them harder to jam from a distance. The military goal was not to make it un-jammable, merely to force a functioning jammer to be so large that it could be found and (ahem) stopped. So GPS was built upon the assumption of radiation-seeking missiles to protect it.
To deter jamming, they spread the main signal SO widely that it was hard for them to even acquire themselves (back in the day). For acquisition they built a less spr

A good question. I dread someone coming up with a reason to jam WiFi personally. If that becomes popular, there are a lot of institutions that have (unwisely IMO) elected to shave costs by allowing their wired infrastructure to crumble, and in some cases decommissioning it entirely. Not to mention the slew of applications which only WiFi and 3G are good for.

Most people I know have a +/- 1KW Wifi jammer. Since it works at about the frequency of a microwave oven you could dismantle one and not only jam a 1 to 2 km radius (guess), but also destroy them in a 200 meter radius (guess aswell). You could even mount it on a parabolic reflector and aim it properly for more range. Of course, you wouldn't want to be near it to switch it on. The radiation would probably mess with your cells.

While Microwaves are, indeed, quite excellent fun(It'd be downright unpatriotic to not like cavity magnetrons: they helped defeat Hitler and provide us with nourishing instant popcorn); but caution is advised.

Shockingly enough, microwaves heat moist things. Like Humans. Now, your body has some degree of liquid cooling built in, handily provided by your bloodstream. However, your Corneas are, shall we say, a bit under-vascularized... Unless you really know what you are doing or don't mind having cataract

If you RTFA, it is likely to screw up the entire Cell Tower, your bank's ATM network at lots of other things you don't expect to rely on GPS. 90% of GPS receivers only use the time signal, and can't operate reliably without it.

If you expect to be able to replace GPS with an Atlas, you won't get to your destination either way.If you're watching a movie or eating in a restaurant where people need GPS, you should probably go somewhere else.

Well my wife is not a nagging sort, but she won't listen to the GPS directions for sure. If it says "Turn right.", she says, "No, that's wrong." and goes her own way. Never gets lost though. She won't go on any expressway or over any tall bridges so she can't follow directions that might take her someplace she won't go. GPS is useless even if I'm driving. By myself I use it all the time.

Yes, and back then they took pagers if they were on call. Before then, they'd leave the address of the cinema with the hospital - if they were needed, the cinema would be called and someone would come and get them from their seat.

You probably don't want one. A few years ago I bought a cell phone jammer from a company in Hong Kong. The build quality was terrible and I was only able to jam phones within a 2 or 3 foot radius at best. Most of the time the phone would drop signal and then find its way back onto the network in 30 or so seconds. I managed just once to drop a stranger's loud call on the train after dozes on attempts.

Turns out cell phones are designed to find ways around interference. Afterall, my jammer was just like having to deal with 100 nearby cell phones trying to make calls. Some phones have no problem with this.

The real issue is that when you're dealing with potentially illegal items with no brands, there's no incentive to make the product work correctly. I wouldn't be surprised if these jammers sucked also.

Just.. um... incidentally... if you want to simply jam GPS, your favorite dodgy Chinese drop-shipper should have what you are looking for by name.

If you want to do anything more elegant or sophisticated in terms of spoofing, they probably won't. However "GPS Simulators" are entirely legitimate pieces of RF test equipment, for use by responsible engineers in closed test environments to evaluate the performance of their GPS-using products against an.. um... "variety of input situations"...

Rental Car companies often track your usage and bill you extra if you leave the state(s) you said you were going to use the rental car in. If you're being tracked by the <insert name of law enforcement agency here> you can render their tracking devices useless. I'm sure there are other opportunities to take advantage of the "stealth mode" offered by such a device.

Lost people tend to cause accidents, and as one does 90% of their driving within a few miles of their home, you or your loved ones/neighbors would most likely to be the victims. Besides what are you going to do, run power out to it? Change the batteries all the time? I'm sure that these little revenge fantasies look much better in your minds eye.

Using a cryptographically secure PRNG seeded from a known time as an authentication token is a well-known, and frequently used technique. For example, many of the "keyfob" type tokens such as the RSA SecureID things. (Which didn't use GPS, and instead used an internal clock and server-based skew tracking if I recall correctly, but the the principle is the same.) I don't know enough about ATMs to weigh in on what schemes they actually use f

The GPS is used to determine the exact time of the transaction. If the time of the transaction at the ATM and the time of the transaction at the Bank differ, then the transaction is refused. I'm not exactly sure why NTP would not be enough, but ATMs using GPS don't use it to find their location.